Asphalt roads may be a larger source of air pollution than cars, study finds.
Scientists have found a 300% increase in harmful particulates emitted from asphalt during hot weather. After study the effect of heat on samples of asphalt, scientists found significant carbon-based emissions.
Researchers from Yale University, Carnegie Mellon University and the Max Planck Institute for Chemistry collected asphalt, commonly found on roads, roofs and driveways. They heated it to temperatures between 40 and 200 Celsius in a tube furnace.
They observed that asphalt emissions doubled when the temperature increased from 40 to 60 Celsius, which are levels the material frequently reaches during summer. The pollutants released were carbon-based chemicals.
‘Many of these compounds are conducive to condensing to form secondary organic aerosol after reacting in the atmosphere,’ co-author Drew Gentner of Yale University commented. Therefore, this can go on to form ultrafine particles known as PM2.5, proven to be particularly detrimental to human health.
The team suspect that asphalt is a significant contributor to air pollution during the summer months.
Pollution from vehicles is beginning to decline in areas as electric slowly replaced petrol and diesel. However, this study shows that air pollution from asphalt could increase. Researchers have highlighted that as climate change causes higher temperatures, more emissions will be triggered by asphalt.
‘We are not making policy recommendations,’ Gentner reinforced, but to understand how much pollution asphalt emits over its lifetime and how it interacts with other sources of pollution. He emphasised that further research was going into ‘cool pavement coatings’ as a way to reduce excess heat in built-up areas.
